This invention relates generally to high-speed line printers employing towel ribbons, and more particularly to a ribbon reverse mechanism for such purpose.
As is well known, high-speed line printers typically comprise a flexible, endless character band, which is located directly in front of a hammerbank assembly including a plurality of print hammers, and which is rotated at a constant speed. In this manner, the characters on the band are successively presented to each hammer, which when energized drives the forms and ribbon against the raised character on the character band to print the selected character. The ribbon, sometimes referred to as a "towel ribbon" is rotated between the a pair of ribbon spools connected to respective drive shafts. Typically comprised of a 3-5 mil nylon material impregnated with ink, the ribbon is wound back and forth between the spools until its ink is depleted.
Prior art high-speed line printers, such as the IBM 1403 typically used a mechanical transmission bar at the end of the ribbon which would engage a ribbon direction sensor and therefore reverse the direction of the ribbon's winding. Other prior art approaches, such as the IBM 3211 printer, utilized a pair of motors with gear reduction (one for a respective spool) in conjunction with an end-of-ribbon bar which would hit toggle switch to change between motors and thereby reverse direction of the ribbon.
One problem with such prior art approaches, however, is the complexity of their transmission mechanisms as well as the duplication of motors required to drive the ribbon between its respective spools. It would, therefore, be desirable to provide a ribbon reverse mechanism which eliminated the requirement for additional drive motors and which simplified the mechanisms necessary to control movement of the towel ribbon.